A new type of enzyme has been discovered in hundreds of bacterial species, and researchers say it helps reveal how bacteria invade organisms. Reporting in Nature Communications, this work may help us understand the mechanisms that underlie bacterial infections, and shows how bacteria use special appendages called flagella for more than just movement.
Led by Andrew Doxey, a Professor of Biology at the University of Waterloo, investigators identified a new kind of flagella. These whip-like appendages are attached to the outside of bacteria and have been thought to be used exclusively for motility. This work shows that another kind of flagellum acts as an enzyme, breaking down proteins that are in the bacteria’s environment. New tools in bioinformatics, which merges biology with computer science, enabled the scientists to make their discovery.
"It is an exciting time for bioinformatics right now. We have thousands of genomes available to us, and most of them are unexplored. It's amazing that we can discover new biology by using a computer alone," noted Doxey. "What we found, in this case, is that many bacteria have repurposed their flagella to function as protein-degrading enzymes. There are thousands of these enzymes, making this potentially one of the largest enzyme structures known."
You can learn more about bacterial flagella, filaments made up of thousands of proteins, from the video. Although there are structural differences in flagella, the majority seem to help move bacteria around, and can also help bind bacteria to host cells. This new work shows how they digest bonds between cells in tissues.
"We think that these enzymatic flagella may help some bacteria degrade and move through viscous environments. Interestingly, scientists have tried engineering flagella with this functionality before, but until now, we didn't know that nature already did this," explained Doxey, who is also a member of the Centre for Bioengineering and Biotechnology at Waterloo.
This work assessed enzymatic flagella that are found in the pathogen Clostridium haemolyticum, which can cause deadly infections in sheep and cows. There are several flagella on each one of these bacterial cells, and they were isolated by the researchers. It was found that these flagella can break down proteins found in the liver of cows, which is exactly where the pathogen initiates an infection.
Bacteria in the human gut also have these types of enzymes, the investigators determined. Additional work will be required before it is known whether these have harmful or beneficial functions in humans.
This discovery may also be useful to humans if they can be harnessed for our purposes. One potential use is for the destruction of harmful bacterial biofilms. These highly pathogenic colonies of microbes can form in troublesome places, including medical equipment, and many researchers are looking for ways to target and destroy them.